A plate filter element usually comprises an even, flat filter body, which is generally produced from a web-like, folded filter material. The filter body thereby usually has a peripheral, lateral edge, which surrounds the cross section of the filter body through which flow passes and has at least two rectilinear edge sections, which border each other, forming a corner. The filter body usually has a rectangular cross section through which flow passes, so that four rectilinear edge section border each other at right angles in four corners. For certain applications, however, polygonal and sometimes rounded edge profiles as well as acute and obtuse angles in the corners are also conceivable. The present invention is concerned with filter bodies which have at least one corner.
In order to be able to arranged the filter body in a filter housing in a leakproof manner, a seal is usually attached to the filter body, which seal is arranged peripherally along the edge of the filter body. This seal can be injection-moulded or foamed or adhesively bonded or welded on. The filter body can likewise be plasticised into the seal.
It has been found that sealing between the filter body and the filter housing is problematic in the corner regions. To avoid leaks, contact between the seal and a corresponding counter contour of the filter housing which is as uniform as possible with the most homogeneous force distribution possible is desired. However, this can be implemented only with difficulty in the corners. If the seal follows the contour of the edge, it has a comparatively small radius on the outside, which greatly impedes a homogeneous sealing effect. If, however, the seal follows a comparatively wide radius, which favours a homogeneous sealing performance, the tight connection to the filter body is made more difficult. If attempts are made to lay the seal in the corner region in such a manner that it has a wide radius on the outside and follows the edge of the filter body tightly on the inside, the corner must be replaced in the corner region by a correspondingly arc-shaped, curved contour. This is however associated with a comparatively large outlay for the production of the filter body, as rectangular outer contours are automatically produced by the folding of the web material. To replace a corner by a rounded portion, complex post-processing of the folded filter body is therefore necessary.